title: Does conditioned taste aversion learning in the pond snail Lymnaea stagnalis produce conditioned fear?
abstract: In conditioned taste aversion (CTA) training performed on the pond snail Lymnaea stagnalis, a stimulus (the conditional stimulus, CS; e.g., sucrose) that elicits a feeding response is paired with an aversive stimulus (the unconditional stimulus, US) that elicits the whole-body withdrawal response and inhibits feeding. After CTA training and memory formation, the CS no longer elicits feeding. We hypothesize that one reason for this result is that after CTA training the CS now elicits a fear response. Consistent with this hypothesis, we predict the CS will cause (1) the heart to skip a beat and (2) a significant change in the heart rate. Such changes are seen in mammalian preparations exposed to fearful stimuli. We found that in snails exhibiting long-term memory for one-trial CTA (i.e., good learners) the CS significantly increased the probability of a skipped heartbeat, but did not significantly change the heart rate. The probability of a skipped heartbeat was unaltered in control snails given backward conditioning (US followed by CS) or in snails that did not acquire associative learning (i.e., poor learners) after the one-trial CTA training. These results suggest that as a consequence of acquiring CTA, the CS evokes conditioned fear in the conditioned snails, as evidenced by a change in the nervous system control of cardiac activity.
authors.affiliation: Science Club, Hokkaido Shiraoihigashi High School, 5-17-3 Hinodemachi, Shiraoi-Cho, Japan.
authors.forename: Serina
authors.initials: S
authors.lastname: Kita
authors.forename: Ryuji
authors.initials: R
authors.lastname: Hashiba
authors.forename: Saya
authors.initials: S
authors.lastname: Ueki
authors.forename: Yukari
authors.initials: Y
authors.lastname: Kimoto
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Abe
authors.forename: Yuta
authors.initials: Y
authors.lastname: Gotoda
authors.forename: Ryoko
authors.initials: R
authors.lastname: Suzuki
authors.forename: Eriko
authors.initials: E
authors.lastname: Uraki
authors.forename: Naohisa
authors.initials: N
authors.lastname: Nara
authors.forename: Akira
authors.initials: A
authors.lastname: Kanazawa
authors.forename: Dai
authors.initials: D
authors.lastname: Hatakeyama
authors.forename: Ryo
authors.initials: R
authors.lastname: Kawai
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujito
authors.forename: Ken
authors.initials: K
authors.lastname: Lukowiak
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ito
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D003214:Conditioning, Classical / Q000187:drug effects; D005239:Fear / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects; D008195:Lymnaea / Q000187:drug effects / Q000502:physiology*; D013649:Taste / Q000187:drug effects; D014481:United States